L1+L2: Fundamental Concepts Flashcards
What are the two types of Voltage Sources and their symbols
How is a Potential Difference formed?
Two unlike charges have a difference of potential or voltage (with symbol V and unit V).
Direction of Charge in different scenarios
Equation for Voltage
Voltage = Energy Spent in Work / Charge
V = W/Q
What is Current?
Current (I) is defined as the rate of flow of electric charge of Intensity of Electricity. The amount of current is dependant on the amount of voltage applied.
What is the equation for Current
Current = Charge/Time
Current Source Symbol
What is Resistance?
Resistance R (unit Ohm Ω) is the opposition to the flow of current.
What does the Power or Wattage rating of a resistor tell us
The Power and Wattage rating of a resistor (in Watts with symbol W) indicates the amount of power it can safety dissipate as heat.
What is Conductance
Conductance is the Inverse of Resistance (with symbol G and unit Siemens, S)
What are variable resistors used for and what are some examples
Variable resistors can vary the resistance value in a circuit. Examples include a Rheostat and Potentiometer
How does Resistor colour coding work
What is Ground Connection in a circuit
Ground Reference is a reference point in a circuit (assumed to have a potential of 0V). Not always grounded to the physical earth.
What are some commonly used ground symbols
How do open and short circuits affect current
- An open circuit prevents current
- A short in a circuit causes more current than normal.
What are Fuses used for
Fuses are used to deliberately create an open circuit when current exceeds a specified amount due to some problem.
How is an electric shock received
- Electric shock is received by touching “live” conductors when power on
- The greatest danger is from high voltage circuits
Electrical safety points to protect yourself
- Resistance of human body is aso an important factor
- When power is on, only use one hand for voltage measurements
- Hand-to-hand shocks can be extremely dangerous
- The best safety rule is to work on cirucits with the power shut off
- Capacitors can stire leatha; charge for long periods even after power shut off
- Keep yourself insulated from earth ground when working on powerline circuits, since one side of the power line is connected to earth ground
What are the Different Directions of Current
What is Direct Current (DC)
Direct current (dc) flows only in one direction
What is Alternating Current (AC)
Alternating current (ac) periodically reverses direction
What happens to resistance and temperature in these graphs
What do Rheostats and Potentiometers do
Rheostats control current in a circuit, and potentiometers are used to divide voltage
Series and Parallel Resistor Circuits info on Voltage, Current, Resistance
Exam Question:
Two resistors of 25Ω and 5Ω, are connected in series to a 240V supply. Calculate the value of a third resistor to be connected in parallel with the 25Ω resistor so that the total power dissipated in the circuit shall be three-times?
